the driver wlan-ng is not included in /lib/modules but is in /opt/drivers which you can put in /lib/modules to verify his functioning.
this is like that to be able to load the driver hostap included in the kernel (default)
modinfo hostap
filename: /lib/modules/2.6.21.5/kernel/drivers/net/wireless/hostap/hostap.ko
if you want to load the driver hostap patched for the injection, execute:
rm /lib/modules/2.6.21.5/kernel/drivers/net/wireless/hostap/*
depmod -a
moprobe hostap_cs
modinfo hostap
filename: /lib/modules/2.6.21.5/extra/hostap.ko